Add a KleeneOp enum for clarity

Author: brendanzab

src/libsyntax/ast.rs

@@ -609,6 +609,14 @@ impl Delimiter {
     }
 }
 
+/// A Kleene-style [repetition operator](http://en.wikipedia.org/wiki/Kleene_star)
+/// for token sequences.
+#[deriving(Clone, PartialEq, Eq, Encodable, Decodable, Hash, Show)]
+pub enum KleeneOp {
+    ZeroOrMore,
+    OneOrMore,
+}
+
 /// When the main rust parser encounters a syntax-extension invocation, it
 /// parses the arguments to the invocation as a token-tree. This is a very
 /// loose structure, such that all sorts of different AST-fragments can
@@ -633,12 +641,9 @@ pub enum TokenTree {
 
     // These only make sense for right-hand-sides of MBE macros:
 
-    /// A kleene-style repetition sequence with a span, a `TTForest`,
-    /// an optional separator, and a boolean where true indicates
-    /// zero or more (..), and false indicates one or more (+).
+    /// A Kleene-style repetition sequence with an optional separator.
     // FIXME(eddyb) #6308 Use Rc<[TokenTree]> after DST.
-    TtSequence(Span, Rc<Vec<TokenTree>>, Option<::parse::token::Token>, bool),
-
+    TtSequence(Span, Rc<Vec<TokenTree>>, Option<::parse::token::Token>, KleeneOp),
     /// A syntactic variable that will be filled in by macro expansion.
     TtNonterminal(Span, Ident)
 }
@@ -711,9 +716,9 @@ pub type Matcher = Spanned<Matcher_>;
 pub enum Matcher_ {
     /// Match one token
     MatchTok(::parse::token::Token),
-    /// Match repetitions of a sequence: body, separator, zero ok?,
+    /// Match repetitions of a sequence: body, separator, Kleene operator,
     /// lo, hi position-in-match-array used:
-    MatchSeq(Vec<Matcher> , Option<::parse::token::Token>, bool, uint, uint),
+    MatchSeq(Vec<Matcher> , Option<::parse::token::Token>, KleeneOp, uint, uint),
     /// Parse a Rust NT: name to bind, name of NT, position in match array:
     MatchNonterminal(Ident, Ident, uint)
 }

src/libsyntax/ext/tt/macro_parser.rs

@@ -323,9 +323,9 @@ pub fn parse(sess: &ParseSess,
             } else {
                 match ei.elts[idx].node.clone() {
                   /* need to descend into sequence */
-                  MatchSeq(ref matchers, ref sep, zero_ok,
+                  MatchSeq(ref matchers, ref sep, kleene_op,
                            match_idx_lo, match_idx_hi) => {
-                    if zero_ok {
+                    if kleene_op == ast::ZeroOrMore {
                         let mut new_ei = ei.clone();
                         new_ei.idx += 1u;
                         //we specifically matched zero repeats.

src/libsyntax/ext/tt/macro_rules.rs

@@ -232,10 +232,11 @@ pub fn add_new_extension<'cx>(cx: &'cx mut ExtCtxt,
         ms(MatchSeq(vec!(
             ms(MatchNonterminal(lhs_nm, special_idents::matchers, 0u)),
             ms(MatchTok(FAT_ARROW)),
-            ms(MatchNonterminal(rhs_nm, special_idents::tt, 1u))), Some(SEMI), false, 0u, 2u)),
+            ms(MatchNonterminal(rhs_nm, special_idents::tt, 1u))), Some(SEMI),
+                                ast::OneOrMore, 0u, 2u)),
         //to phase into semicolon-termination instead of
         //semicolon-separation
-        ms(MatchSeq(vec!(ms(MatchTok(SEMI))), None, true, 2u, 2u)));
+        ms(MatchSeq(vec!(ms(MatchTok(SEMI))), None, ast::ZeroOrMore, 2u, 2u)));
 
 
     // Parse the macro_rules! invocation (`none` is for no interpolations):

src/libsyntax/ext/tt/transcribe.rs

@@ -227,9 +227,9 @@ pub fn tt_next_token(r: &mut TtReader) -> TokenAndSpan {
                 r.stack.last_mut().unwrap().idx += 1;
                 return ret_val;
             }
-            TtSequence(sp, tts, sep, zerok) => {
+            TtSequence(sp, tts, sep, kleene_op) => {
                 // FIXME(pcwalton): Bad copy.
-                match lockstep_iter_size(&TtSequence(sp, tts.clone(), sep.clone(), zerok), r) {
+                match lockstep_iter_size(&TtSequence(sp, tts.clone(), sep.clone(), kleene_op), r) {
                     LisUnconstrained => {
                         r.sp_diag.span_fatal(
                             sp.clone(), /* blame macro writer */
@@ -243,7 +243,7 @@ pub fn tt_next_token(r: &mut TtReader) -> TokenAndSpan {
                         }
                     LisConstraint(len, _) => {
                         if len == 0 {
-                            if !zerok {
+                            if kleene_op == ast::OneOrMore {
                                 // FIXME #2887 blame invoker
                                 r.sp_diag.span_fatal(sp.clone(),
                                                      "this must repeat at least once");

src/libsyntax/parse/parser.rs

@@ -2497,27 +2497,30 @@ impl<'a> Parser<'a> {
         return e;
     }
 
-    /// Parse an optional separator followed by a kleene-style
+    /// Parse an optional separator followed by a Kleene-style
     /// repetition token (+ or *).
-    pub fn parse_sep_and_zerok(&mut self) -> (Option<token::Token>, bool) {
-        fn parse_zerok(parser: &mut Parser) -> Option<bool> {
+    pub fn parse_sep_and_kleene_op(&mut self) -> (Option<token::Token>, ast::KleeneOp) {
+        fn parse_kleene_op(parser: &mut Parser) -> Option<ast::KleeneOp> {
             match parser.token {
-                token::BINOP(token::STAR) | token::BINOP(token::PLUS) => {
-                    let zerok = parser.token == token::BINOP(token::STAR);
+                token::BINOP(token::STAR) => {
                     parser.bump();
-                    Some(zerok)
+                    Some(ast::ZeroOrMore)
+                },
+                token::BINOP(token::PLUS) => {
+                    parser.bump();
+                    Some(ast::OneOrMore)
                 },
                 _ => None
             }
         };
 
-        match parse_zerok(self) {
-            Some(zerok) => return (None, zerok),
+        match parse_kleene_op(self) {
+            Some(kleene_op) => return (None, kleene_op),
             None => {}
         }
 
         let separator = self.bump_and_get();
-        match parse_zerok(self) {
+        match parse_kleene_op(self) {
             Some(zerok) => (Some(separator), zerok),
             None => self.fatal("expected `*` or `+`")
         }
@@ -2564,11 +2567,11 @@ impl<'a> Parser<'a> {
                         seq_sep_none(),
                         |p| p.parse_token_tree()
                     );
-                    let (s, z) = p.parse_sep_and_zerok();
+                    let (sep, repeat) = p.parse_sep_and_kleene_op();
                     let seq = match seq {
                         Spanned { node, .. } => node,
                     };
-                    TtSequence(mk_sp(sp.lo, p.span.hi), Rc::new(seq), s, z)
+                    TtSequence(mk_sp(sp.lo, p.span.hi), Rc::new(seq), sep, repeat)
                 } else {
                     TtNonterminal(sp, p.parse_ident())
                 }
@@ -2679,8 +2682,8 @@ impl<'a> Parser<'a> {
                 if ms.len() == 0u {
                     self.fatal("repetition body must be nonempty");
                 }
-                let (sep, zerok) = self.parse_sep_and_zerok();
-                MatchSeq(ms, sep, zerok, name_idx_lo, *name_idx)
+                let (sep, kleene_op) = self.parse_sep_and_kleene_op();
+                MatchSeq(ms, sep, kleene_op, name_idx_lo, *name_idx)
             } else {
                 let bound_to = self.parse_ident();
                 self.expect(&token::COLON);

src/libsyntax/print/pprust.rs

@@ -1037,20 +1037,23 @@ impl<'a> State<'a> {
                     _ => Ok(())
                 }
             }
-            ast::TtSequence(_, ref tts, ref sep, zerok) => {
+            ast::TtSequence(_, ref tts, ref separator, kleene_op) => {
                 try!(word(&mut self.s, "$("));
                 for tt_elt in (*tts).iter() {
                     try!(self.print_tt(tt_elt));
                 }
                 try!(word(&mut self.s, ")"));
-                match *sep {
+                match *separator {
                     Some(ref tk) => {
                         try!(word(&mut self.s,
                                   parse::token::to_string(tk).as_slice()));
                     }
                     None => ()
                 }
-                word(&mut self.s, if zerok { "*" } else { "+" })
+                match kleene_op {
+                    ast::ZeroOrMore => word(&mut self.s, "*"),
+                    ast::OneOrMore => word(&mut self.s, "+"),
+                }
             }
             ast::TtNonterminal(_, name) => {
                 try!(word(&mut self.s, "$"));